In patent document 1, there is disclosed a technology where, when data such as a user program and the like are written in a user memory area of a flash memory, a flash firmware and a parameter of a default and flash identification information are stored in advance in a mask memory area of a mask ROM, version information or lot information is stored in a non-volatile memory and a CPU selects and carries out an optimum flash firmware and a parameter based on the version information, a rewrite process to the flash memory can be carried out under the optimum condition.
In patent document 2, there is disclosed a technology that has an EEPROM for data and an EEPROM for program, stores a locking code in a designated area, and, by making use of the locking code, inhibits price data or programs stored in a rewritable memory such as the EEPROM for data and the EEPROM for program from being altered.    Patent Document 1: JP-A-2001-306543    Patent Document 2: JP-A-2002-245023